What are the best nutrients for autoflowers?

Autoflowering seeds have a long list of advantages over photoperiod strains including their ability to flower automatically, their robustness and the speed at which they can finish. However, they still lack in size when compared with photoperiods and because of this they also require slightly different nutrients and a different feeding schedule. So, if we want to achieve the best possible yields, what are the best nutrients for autoflowers?

What are the benefits of growing autoflowers?

Despite their size autoflowers are becoming increasingly popular and this is because of the convenience that they offer. But what are the main reasons that people grow autoflowering strains?

  1. Faster growth: Autoflowers have a shorter life cycle, taking just 8-10 weeks to mature from seed to harvest.
  2. Ease of growth: Autoflowers do not require a change in light cycle to switch from vegetative to flowering stage, making them easier to grow.
  3. Discretion: Autoflowers are smaller and less noticeable than photoperiod strains, making them a good choice for stealth grows.
  4. Good yield potential: With their shorter life cycle, autoflowers can produce multiple harvests in a single growing season.
  5. Versatility: Autoflowers are incredibly robust and hardy strains, they can be grown indoors or outdoors in a variety of climates and are suitable for a variety of growing setups.

Can you use nutrients on Autoflowers?

This is a common question that gets asked by a lot of first-time growers. The answer is yes, all cannabis plants require nutrients, without them they will die. However, there are two main types of nutrients, synthetic and organic. I think this question stems from the fact that many growers overfeed autoflowering strains using synthetic feed resulting in nutrient burn or in some cases causing their plants to die. 

Put simply, not only can you give autoflowers nutrients, they need them to survive. Nutrients should not be given to any cannabis plants, photoperiod or autoflower, for the first couple of weeks. But beyond this point they will need a regular supply of nutrients to grow. More on this though further in the article….

What nutrients do I need for Autoflowers?

Most nutrient brands you will find on the shelves of your local grow shop will be designed for photoperiods. Autoflowering strains need the exact same nutrients that photoperiods require, the main difference is the amount they need is less. 

Autoflowers are much smaller than photoperiods so the nutrients need to be adjusted to accommodate this. They also have much shorter vegetative and flowering periods so the nutrient feeding schedules will need to follow a slightly different life cycle. 

What are the main nutrients that cannabis plants require?

  1. Nitrogen (N): Promotes vegetative growth and healthy leaves.
  2. Phosphorus (P): Supports root growth and flower development.
  3. Potassium (K): Helps regulate water uptake and promotes overall plant health.
  4. Calcium (Ca): Supports strong cell walls and helps prevent deficiencies.
  5. Magnesium (Mg): Essential for chlorophyll production and helps with nutrient uptake.

Unless you are using a specific nutrient blend that is made for autoflowering strains you will need to dilute the nutrients down to avoid burning your plants. Because of their shorter life cycle and smaller size go easy when feeding your autos and always start off slow. Less is more when feeding autoflowers. Remember, you can always add more nutrients but once it is in the soil you can’t take it out.

Autoflower feeding schedule

There is no one set nutrient schedule for all strains as some plants are heavier feeders than others. However, this is a good feeding schedule that can be applied to pretty much all autoflowering strains. With a little more experience growing you may find that your particular autoflower responds well to a certain nutrient during a particular stage, in which case you can adjust the schedule accordingly. You should also do some research on the cannabis strain you are growing, in general indicas take more food than sativas. However, stick to this schedule to start with and adjust according to the plant’s response.

WeekGrowth StageNutrients
Week 0 – 2Germination/seedlingNo Nutrients
Week 2Early veg⅛ Veg nutrients
Week 3Vegetative stage¼ Veg nutrients
Week 4Vegetative stage¼ – ½ Veg nutrients
Week 5Preflowering stage¼ veg + ⅛ bloom nutes
Week 6Early flowering stage¼ bloom + ⅛ veg nutes
Week 7Flowering stage¼ bloom nutrients
Week 8Flowering stage½ bloom nutrients
Week 9Late flowering stage½ bloom nutrients
Week 10Late flowering stage⅛ bloom nutrients
Week 11FlushingPlain water

What does Epsom salt do for Autoflowers?

Epsom salts come from a natural spring in a town called Epsom. They are a naturally occurring type of salt that is full of magnesium and sulfur and famed for its healing properties.

Epsom salts help cannabis plants by providing a high dosage of sulfur and magnesium. Magnesium aids the absorption of nitrogen (N), phosphorus (P) and potassium (K) in plants and plays a key role in photosynthesis. Cannabis plants suffering from magnesium deficiencies display tell-tale signs of yellowing leaves and shoots with stems becoming purple in extreme cases. 

The wonderful thing about Epsom Salts is that they provide a completely natural dose of magnesium and sulfur to your plants. This not only prevents magnesium deficiencies but also acts as a boost to the plants immune system promoting good overall health.

How do you fatten autoflower buds?

There are two main aspects to growing big fat buds on your autoflowers. One is training your autos using either LST or HST plant training methods (LST is best suited for autoflowers). The other is using the right cannabis nutrients at the right time to boost bud production during the flowering stage. All cannabis plants require a heavier dose of phosphorus (P) and potassium (K) to aid growth as their bud’s bloom. Potassium helps a plant to grow its buds and phosphorus strengthens a plant and supports its roots. Nitrogen is the key ingredient needed for growing a denser foliage, this should be reduced during the flowering stage to encourage the plant to focus on bud production. Using nutrients during the flowering stage that have similar ratios to those in the NPK ratio chart below will help you to increase bud size.

For those of you that are growing autoflowers organically, you can use natural fertilizers such as bat guano as a soil dressing during the flowering stage. Simply sprinkle a layer or bat guano on top of the soil surrounding your plant at the start of the flowering stage. Then each time you water your plants the nutrients will drain down through the soil creating a nutrient rich organic solution for your plants.

Ideal NPK ratios for autoflowers

Growth StageNPK Ratio
Weeks 1-2Plain pH’d water
Early veg stage4-2-3
Vegetative stage10-5-7
Late vegetative stage7-7-7
Early flowering stage5-10-7
Flowering stage5-15-10
Late flowering stage4-10-7
Last weekFlush with pH’d water

What are the signs of nutrient burn in cannabis?

You need to be particularly careful when feeding autoflowers, because of their size, nutrient burn is much more common that with photoperiods. If you are worried that you may have overdone it with the feed, here are a few telltale signs that your plants could be suffering from nute burn.

  1. Leaf Discoloration: The first and most obvious sign of nutrient burn is a yellowing or browning of the leaves, usually starting at the tips and moving inward. This discoloration is a result of the excess nutrients overwhelming the plant’s ability to absorb them.
  2. Leaf Curling: Another tell-tale sign of nutrient burn is the curling of the leaves. This is caused by the plant trying to conserve moisture, as the excess nutrients in the soil can cause the roots to dry out.
  3. Stunted Growth: Nutrient burn can also lead to stunted growth, as the plant’s energy is redirected away from its growth and towards dealing with the excess nutrients.
  4. Leaf Necrosis: In severe cases, nutrient burn can cause leaf necrosis, the death of the plant’s leaves. This is a sign that the plant is struggling to cope with the excess nutrients and is in a state of distress.

Remember, prevention is key, and it is essential to carefully monitor the nutrients in your soil and adjust as necessary to avoid this common problem.

Organic nutrients vs synthetic nutrients for autoflowers

Growing autoflowers with organic nutrients involves creating a soil that is filled with tiny microorganisms that create a nutrient rich environment for your plant to live. The organic nutrients either found in the soil or added to it are broken down by the microorganisms and easily absorbed by the cannabis plant. You can grow autoflowers in a soil that is made up of compost, worm castings and bat guano. These create a self-sustaining environment that should provide enough nutrients for your autoflower from seedling right the way through to harvest.

cannabis seedling in pot with soil and coco coir mixture

Benefits of using organic cannabis nutrients:

  1. Healthier plants: Organic nutrients come from natural sources and are free from harmful chemicals, leading to healthier and stronger plants.
  2. Better taste and smell: Organic nutrients can improve the taste and aroma of weed because they help to produce terpenes, which are the compounds responsible for the smell and flavor of cannabis.
  3. Environmentally friendly: Organic nutrients are made from natural ingredients, which are biodegradable and do not harm the environment.
  4. Safe for consumption: Organic nutrients are free from harmful chemicals and are considered safe for consumption.

Negatives of using organic cannabis nutrients:

  1. Cost: Organic nutrients can be more expensive compared to synthetic ones.
  2. Availability: Organic nutrients may be harder to find, especially if you live in an area with limited access to natural resources.
  3. Time-consuming: Organic nutrients require more preparation and may take longer to see results compared to synthetic ones.
  4. Inconsistent results: Organic nutrients can be more difficult to control and measure, leading to inconsistent results in terms of plant growth and yields.

Synthetic nutrients on the other hand are delivered to the plant when you water them. This can either be done through dissolving the nutrients into water and then pouring onto the soil or plant. Alternatively plants can be fed using hydroponic methods where the nutrients are dissolved in a reservoir of water that is then continuously supplied to the roots of a plant.

Benefits of using synthetic cannabis nutrients:

  1. Convenience: Synthetic nutrients are easy to use, as they come in pre-measured formulas, and are readily available in most grow stores.
  2. Consistency: Synthetic nutrients provide consistent results, as they contain specific amounts of macro and micronutrients that are necessary for plant growth.
  3. Cost-effective: Synthetic nutrients are often less expensive compared to organic ones.
  4. Ease of measurement: Synthetic nutrients are easy to measure and control, as they come in pre-packaged formulas.

Negatives of using synthetic cannabis nutrients:

  1. Health risks: Synthetic nutrients can contain harmful chemicals and contaminants that can be toxic to plants and humans.
  2. Environmental impact: Synthetic nutrients can harm the environment, as they are not biodegradable and can leach into soil and water.
  3. Reduced aroma and taste: Synthetic nutrients may not enhance the aroma and taste of the final product like organic nutrients can.
  4. Dependence: Plants may become dependent on synthetic nutrients, making it difficult to switch to an organic fertilizer program.

What nutrients are best for autoflowers?

Organic nutrients can be used to grow any type of cannabis plant; however, they are particularly useful when it comes to growing autoflowers. Autoflowers are much smaller and therefore require a lot less nutrients than your average photoperiod. One of the main risks of using synthetic nutrients is over feeding your plants and causing nutrient burn. With organic nutrients you don’t have this risk because instead of feeding the plant with a dissolved nutrient mix, the plant takes the nutrients from the soil as and when it is needed. Although synthetic nutrients work faster, we feel that the positives of organic growing outweigh the negatives, particularly when it comes to growing autoflowers. If you are a beginner and find all of this information a little bit confusing, try using the organic fertilizers explained below for a straightforward approach.

How can you make autoflowers more potent?

To make your autoflowers more potent you need to ensure they are producing as much THC as possible. It may seem like a vague answer but to do this you need to make sure every aspect of your cannabis grow is as good as it can be. From providing good quality light, soil, nutrients, and making sure your plants are all around a picture of health, will mean that they are optimized for producing THC. Once you have happy cannabis plants that are growing as they would be in the wild, you have done all that you can to encourage the plant to produce THC. However, there is one more trick that many first time growers may not know….

During the final stages of flowering all cannabis plants have a 2 week window when they contain the highest amount of THC. Harvest during this window and your bud will certainly be more potent. For more information on this, read our full guide on how to harvest weed for optimum potency

One last thing that should not be overlooked is the process of harvesting itself. Harvesting weed isn’t as simple as cutting down your plants, trimming the bud and then smoking it. A proper and thorough harvest involves drying weed for up to 7 days, followed by curing it for a further 30 days. Drying and curing your bud helps to preserve the cannabinoids (this includes THC) and terpenes within your bud. This process may be tempting to skip when you have just spent 10 weeks growing your precious bud. But carefully drying and curing weed will not only improve potency but also the taste too.

Best organic nutrients for autoflowers

Ah, the question of what the best organic nutrients for cultivating cannabis are. Well, it is difficult to give an answer that everyone will agree on but let me share with you some of my favorite options.

  1. Compost tea: This elixir is made from decomposed organic matter, such as leaves and vegetable scraps, and is rich in beneficial microorganisms that nourish the soil and promote healthy plant growth.
  2. Bat guano: This nitrogen-rich fertilizer is derived from bat excrement and has been used for centuries to support the growth of crops. It is a slow-release fertilizer, providing a steady supply of nutrients to the plant.
  3. Worm castings: These nutrient-rich balls of excrement are produced by earthworms and are a fantastic organic fertilizer for cannabis plants. They contain a wealth of essential nutrients, including nitrogen, phosphorus, and potassium.
  4. Bone meal: This fine powder is made from steamed animal bones and is an excellent source of phosphorus, an essential nutrient for healthy root development.

You can easily create your very own organic soil mix at home using some of the ingredients listed above. Visit our guide on how to make the best soil for your autoflowers for a great DIY soil recipe.

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